Telephone system.



G. S. WINSTON.

TELEPHONE SYSTEM.

APPLICATION FILED SEPT. 9, 1912.

1,1 08,482. Patented Aug. 25, 19m

4 SHBETSSHEET l.

ZZZUZZEZZ G. S. WINSTON.

TELEPHONE SYSTEM.

APPLIOATION FILED SEPT. 9, 1912.

1,1 08,482 Patented Aug. 25, 1914;

4 SHEETS-SHBET 2.

C. S. WINSTON.

TELEPHONE SYSTEM.

APPLICATION FILED SEPT. 9, 1012.

1,1 08,482. Patented Aug. 25, 19m

4 SHEETS-SHEET 3.

MI W

Ihm" [E5 SZ/ Z/z'zz5ZZ7z2 @M 5 2 V J E 2i M EUbrzzegz C I! i G. S.WINSTON.

TELEPHONE SYSTEM. APPLICATION FILED SEPT. 9, 1912.

Patented Aug. 25, 1914,

4 SHEETS-SHEET 4.

Jim/E2752": .ZfiEZZES 52/ 2222572722 fiffarz z W W Q ay; duh

r nois, have invented certain new and useful UNITED STATES PATENTOFFICE.

OHARLES S. WINSTON, OF CHICAGO, ILLINOIS, ASSIG-NOR TO KELLOGGSW'I'RGHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OFILLINOIS.

TELEPHONE SYSTEM.

To all whom it may concern Be it known that I, CHARLES S. WmsToN, acitizen of the United States, residing in Chicago, county of Cook, andState of Illi- Improvements in Telephone Systems, of which the followingis a specification.

My invention relates to telephone systemsin which automatic switches areemployed for extending connections, the switches being of what is knownas the two dimension type, comprising a bank of contacts divided intogroups, and cooperating wipers adapted to be primarily adjusted toselect a group, and thereafter secondarily adjusted to select a contactin a group.

My invention has to do more particularly with systems of the abovecharacter in which metallic control circuits for the switches areprovided, thus eliminating the use of a ground at the control or impulseapparatus.

In previous systems of the above charac ter, slow acting relays havebeen employed for controlling the secondary and release movements of theswitch. That is, slow acting relays have been employed in conjunctionwith a quick acting primary or impulse relay, and in such systems, dueto the fact that the energizing circuit for the re lease and secondaryrelays is rapidly interrupted when the primary relay is operated fortransmitting primary impulses, these release and secondary relays havebeen of a special construction in order to maintain their armaturesattracted duri such primary relay operations, and to this end a coppersleeve about the core or a no-n-inductive winding connected in multiplecircuit with the winding of said relays is ment in this direction aswill be more clearly pointed out.

For a more complete understanding of my invention reference is to be hadto the accompanying drawings, in which like refercnce charactersindicate like parts, and in which Figure 1, comprising parts 1, 2 and 3,

Patented Aug. 25, 1914.

illustrates a so'called complete automatic telephone system; 2illustrates diagrammatically a mechanical line switch adapted station Fwith its associated switch B also being illustrated. In a fullinstallation of Ra system as referred to, there would be 10,000substations A each connected by a line L with its associated line switchB of iw'hich there would be 10,000. These lines and switches B would bedivided into ten 3 major groups of 1000 each, and each major group wouldbe divided into minor groups iof 100 each. On a basis of ten per cent.

trunking there would be provided 1000 first fselcctors C, divided into100 groups of 10 leach, each group of 10 being assigned to a minor groupof 100 line switches B. All of the line switches B of each minor groupwould have access to its associated 10 first selectors C, and to thisend'each ten selec- Etors C wou-ldbe multiply connected to the ibaukcontacts of the associated 100 line switches B, although in Fig. 1 buttwo such f multiple connections are shown.

E On a basis ct ten per cent. trunking as previously refierred to, theselector and connector switches employ 100 sets of bank con tacts J(Fig. 3) divided into ten groups of ten contact sets each,.and thecooperating wiper set W may be primarily adjusted to select one of thegroups or rows of contacts, and thereafter secondarily adjustedto selecta contact set in a group. Therefore on the basis outlined, one thousandsecond selectors D would also be provided, being divided into 100 groupsof ten second selectors each, and each such group of ten secondselectors D would have its wipers multipled betore the bank contacts of1:00 first selectors C,

each such one hundred first selectors C comto operate in connection withline switch prising preferably ten groups of ten first selectors each,these ten groups being the corresponding hundred or minor groups of theten major groups. In other words, take the ten first selectors in thefirst hundred groups of each of the ten one thousand or major groups.The first rows J (Fig. 3) of these ten minor groups would be multiplyconnected, the second rows J would be multiply connected, etc., up toand including the tenth group J. The first groups J of multiplyconnected contacts would then be connected to the wipers of the tensecond selectors D assigned to the first hundred group of the firstthousand or major group,-

the second groups J 2 would be assigned to the second selectors D in,the second major group and so on. A like arrangement of multiplyingwould then be given to the ten second hundredths groups, etc. suming asubscriber wished to connect with a line in the third thousand group,the first operation of his calling device would result in three primarysteps of wipers W (Fig. 3) of a selected first selector to pick out thethird group J which is the group of contacts leading to second selectorsD in the third thousand group and thereafter wiper K would automaticallyselect an idle one of these second selectors D.

From the above it will be seen how by the operation of a first selectorD, access will be had by a calling subscriber to the thousand or majorgroup including the line of the called substation. On the samepercentage of trunking as outlined above, one thousand connectors Eareprovided, divided into one hundred groups of ten connectors each, eachsuch group being assigned to a different one hundred group of lines.Each group of ten connectors has its wipers connected to the tencorresponding groups J of the second selector bank contacts in the sameone thousand group. In other words, take the group of ten connectorsassigned to the first hundred group of lines, inthe first thousandgroup. These connectors would have their wipers multiply connected tothe first row J of bank contacts of the one hundred first selectors inthe same thousand group. The group of connectors E assigned to thesecond hundred group of the first thousand group would then be multiplyconnected to the second rows or groups J 2 of the second selectors inthe same thousand groups, and so on to the tenth group of connectors.This same method of multiplying the connectors it would also obtain inall of the other major groups. Each such group of ten connectors E wouldthen have its bank contacts multiply connected to the associated onehundred lines. Thus with the foregoing outline, assume a subscriberdesired to connect ,with telephone number 1234. After picking out anidle first selector C he-would efi'ect one Thus as-- primary step of itswipers W to select the first group J of bank contacts, which group wouldlead to second selectors D in the first thousand or major group oflines, which group includes the line of the called subscriber.Thereafter the first selector would automatically pick out one of theten second selectors D connected to this first group J The subscriberwould then effect two steps of the wipers W of the selected switch 1),thereby picking out the second group J 2 which is connected toconnectors E in the second hundred group including the line of thecalled substation. Thereafter switch D would automatically select anidle one of the connectors. The calling subscriber would then efi'ectthree primary steps of the Wipers WV of the selected connector E pickingout the third group J which group includes the terminals of the calledsubstation, and thereafter four steps of wipers W would be effected toselect the fourth set of contacts in the selected group J whichcontacts" are the terminalsof the called line.

While the above trunking and grouping arrangement is well known in theart, it has been herein described that an understand ing of a trunkingarrangement suitable for the embodiment of my invention herein shown,may be had. It will be understood that the trunking arrangement is notinvariable and that other arrangements may be used, according to theexigencies wherein my inventionmay be employed.

Referring now more in detail to the apparatus and circuit arrangementpreferably employed in this embodiment of my invention, substations Aare of the well known Kellogg type having a calling device 1 with itsinterrupter contacts 2 connected in circuit with the line conductors,the impulse wheel 3 being so arranged that when advanced, its teeth willnot interrupt the contacts 2 but upon being restored by its spring itwill interrupt said contacts 2 according to the number of teeth on itsperiphery which were initially moved beyond said contacts. The line Lcomprising line conductors 4 and 5 extends from substation A to its lineswitch B. Line switch B comprises a line relay LR, cut-ofi relay CO,motor magnet M, offnormal contacts ON, and a pair of line wipers 9and'12. and cooperating contacts being normally in engagement withratchet 6 while pawl 8 is normally out of engagement with said ratchet.In the preferred operation of Fig 2, which is in accordance with circuitB, upon initiation of a-call by removal of the receiver from the switchhook, line relay LR is energized thus causing the associated pawl 8 toengage ratchet wheel 6 and thereafter cuteofi' relay CO is energizedcausing its associated ratchet 7 to disengage from ratchet wheel 6.Thereafter the motor magnet ll/l advances the wipers over the contacts,followed by the deenergization of GO, but LR is maintained energized sothat both pawls 7 and 8 are engaging ratchet 6. To release switch B linerelay LR is deenergized, thus Withdrawing pawl 8 from enga ement withratchet 6 and thereafter cut-ofl relay CO is again energized moving pawl7 out of engagement with ratchet 6, allowing the wipers to be restoredby a suitable spring. Un the first step oft-normal, contacts ON assumetheir alternate position and are maintained thus until the wipers are restored, whereby said contacts ON are again moved to their normalposition. Other forms of line switches maybe employed without in any wayad'ecting the principle or operation or my invention.

ln 3 l have illustrated diagrammatically the contact bank and wiperarrangement of one term of selector and connector switch that may beused with my invention,

arranged in ten vertical groups l d il etc, to J, ten sets in eachgroup. Each set consists ct three contacts 34-, 35 and as, (which forclear illustration l have spread apart at the lirst row in Fig. 3, andwhich correspond to contacts 34, 35 and .86 in Fig. 1, part 1). A set ofwipers W consisting of wipers 81, 3% and 33 are provided to wipe overthe corresponding contacts in the till vertical groups. ("llliesemagnetwipers cor respond to wipers 31, 32 and 33 in ll igd, part 1). it.primary magnet (P. M, Fig.

1, part 1) is adapted to rotate the wipers through the medium ot" aprimary shaft PS tov bring them opposite one oi? the vertical groups ofcontacts. lhis group selecting movement is in response to directiveimpulses sent over the line fromthe subscribers station. A secondarymagnet (S. M. Fig. 1, part 1), is provided to step the wipers in avertical direction through the medium of a secondary shaft SS to selectan idle contact set in the selected group. This secondary movement toselect an idle set of contacts in the selected group in the selectors isaccomplished automatically, without the aid of directive impulses fromthe subscribers station. The switch construction is preferably such thatthe wipers are advanced against the tension of a pair of so-called watchsprings, one spring opposing each movement respectively.

To release the switch wipers, and restore them to normal position afterconnection with one of the sets oi contacts in a group, the secondarymagnet is again actuated to step the wipers beyond the last or topcontact of that group, whereby they are automatically restored to normalby the springs referred to, the wipers in being restored taking the pathindicated by arrows in Fig. 3. Thus, in the operation of the switch thecontacting ends of the wipers travel in a primary direction (horizontalrotary) to select a group oi contacts, then in a secondary dlrection(vertical rotary) to select a contact in that group, and in the releaseof the wipers this secondary travel is continned until the contactingends have passed beyond the last or'top contact in the group, when theyare automatically releasedas shown by the arrows to normal position.

it set of primary oil-normal spring con tacts POhl are moved upon thefirst primary step of the switch while a set oi secondary ofi-normalspring contacts Fitll l are moved upon the first secondary step of theswitch, being restored upon restoration of the wipers from theirrespective movements as will be clear trom the diagram.

lit is to be understoodthat tor a more detailed description oit thisswitch, retorence is to be had. to the above identified application.

l irst selector tl comprises, besides its wipers and 'banlr contacts, aprimary magnet PM, a secondary magnet illltl, a primary or impulse relayPR adapted to be energized by current over a calling line uponconnection'made with said switch U, a main release relay R which isadapted to be energized responsive to the initial energization of relayll lt, a release relay RR adapted to be energized responsive to theinitial energiza ."lllti tion oil MRlt, and a secondary relay Slitadapted to be energized following the energiuation of ltlt. A. testrelay Tit is also provided being adapted to be energized to efiec't asecondary-travel of the switch to select an idle set of contacts in theselected grou 4 preferably arrange magnets SR ,and i so that theresistance and self-induction of SR is greater than that of PM so thatwhen current impulses flow through the windings of these magnets inmultiple, upon the interruption of such flow, due to 5 the greaterself-induction of SR, the selfinduced current of SR flows through theclosed circuit including magnet PM and therefore maintains the armatureof SR attracted between impulses. Second selector D (Fig. 1,-part 2). ispreferably the same construction as the first selector, and compriseswipers and suitable bank contacts, operating magnets PM SM, a releaserelay RR and test relay Off-normal switches PON and SON are alsoprovided. The relation between magnets PM and SR of this switch ispreferably the same as the corresponding magnets of first selector 0..Connector switch E is also of the same construction,

and comprises besides its wipers and cooperating contacts, oil-normalswitches PON and SON, operating magnets PM SM secondary relays SR SRrelease relays RR RR switching relay SW, a line test relay LT, a relayH, controlled by relay LT and maintained energized while LT isenergized, a. flip-flop or interrupter relay FF for intermittentlyconnecting ringing generator G and thebridged control relay CR acrossthe terminals of the called line, adisconnect relay DR for disconnectingthe ringing current upon response of the called subscriber, a circuitclosing relay CL also energized when a called subscriber responds, and atest conductor interrupter relay TI. In this switch the relay SR isfirst connected in multiple with PM and thereafter with SM so thatmagnets PM and SM are related to relay SR like that of the first andsecond selector switches.

The called line L1, called sub-station F" and associated line switch Bare similar to thecallin line equipment, the similar parts 5 beingindicated by like reference characters but with the sufiix prime.

Operation of Fig. 1.'-Having described in general theapparatus andcircuit arrangement in the preferred embodiment of my invention, theoperation of the system illustrated, in connecting a calling and calledline, will now be described. Assuming a subscriber at station A desiresto connect with a'subscriber at substation F whose telephone number wewill assume is 2343, he,

. 5 contact ON. Relays and CO being en- 'ergized, a circuit for motormagnet M is es-..

tablished through their alternate contacts 14 and 15 respectively,whereby said magnet M advances wipers 9, 12 and 16 into engagement withthe first set of contacts 17, 7 18, 19, which, we will assume leads to abusy first selector C. This first trunk being busy,

it has a ground or busy potential connected to its contacts 19 from theassociated first selector in a manner as will be described. A

locking circuit for relays LR and CO is ON at the first step of theswitch. Magnet M now advances the wipers another step and in factcontinues such advancement until the test wiper 16 reaches an idle testcontact 19 which we will assume is the third one leading to the firstselector C. This being idle, as stated, it would be ungrounded andtherefore the locking circuit for relays LR' and CO is interrupted, butrelay LR being a slow acting relay maintains its armature attracteduntil a locking circuit from switch C is provided, which will be laterdescribed, but relay CO being a quickacting relay immediately releasesits armature opening its contact 15 in the circuit of driving magnet M,thus rendering the switch wipers inert. As above stated L is one of a103 group of lines that has access to a group of ten first selectors C,and thus the first idle selector C of the group is automaticallyselected by the removal of the receiver from ishe hook of any one ofsaid group of 100 105 lnes.

Due to the closing ofnormal contacts 10, 11 of relay CO when it isdenergized, a circuit for the primary relay PR of the selector C isestablished over the calling line, which may be traced from groundthrough the left end winding of PR, the upper heavily marked primaryconductor, contact 18,

wiper 12, normal contact 11, the calling line and substation, normalcontact 10, wiper 9, the selected contact 17 and the right end windingof PR to battery, causing its energization. PR is the relay energizedover the subscribers line, which responsive to a single series ofdirective impulses from the sub- 12o scribers station, effects theoperation of magnet PM to move the wipers of the first selector to agroup of contacts. The wipers are then automatically driven to select anidle contact in the group without the send- 1% ing of further impulsesfrom the subscrib ers station.

Upon the closing of alternate contact22 of PR, the locking circuit abovereferred to for the slow-acting line relay LR is estab-.

' nate contact 23, and the winding of MRR to lished, traced overxcontact 19, wiper 1.

ternate contact 20, and the winding of LB to battery thus maintainingsaid relayenergized until a release is desired. Also re; .sponsive toenergization of PR, its alternate contact 23 closes, establishing acircuit or main release relay MRR, traced from ground at normal contact24 of PON, alterbattery, whereby said relay is energized, closing itsalternate contact 25, whereby ground from said alternate contact 25 issubstituted for holding the circuit through MRR.

after the interruption of the normal contact 24 upon the first step ofthe switch. Also responsive to energization of MRR, its alternatecontact 26 is closed, establishing an energizing circuit through relayRR, whereby it attracts its armature.

In the present system as well as two wire systems of the past, whichrelate to two dimension switches, it is essential that the release relaybe maintained energized during the operation of'the primary relay insending the directive impulses, although the cirrelay, these being wellknown expedients.

In a priorapplication of mine, have elimi nated the use of such slowacting release relays by providing two paths for current through therelease relay, one of which is controlled through contacts of theprimary relay, and the other of whichwas preferably controlled throughcontacts on the re lease relay, the second path being of comparativelylow current value, lout sufficient to maintain the armature of therelease relay attracted while its first circuit was being rapidlyinterrupted by .the primary relay.

In the present application, I provide such a second path ofconrparatiyely low current value for the main release relay, but controlit through a second so-called release relay RR, this second pathincluding alternate contact 27 and high resistance winding 28 to ground.This second circuit is so proportioned that the current flowingtherethrough will he sufiicient to maintain the armature of MRRattracted, while the first energizing circuit therefor is being rapidlyinterrupted at alternate contact 23 of RR. This will be more-clearlybrought out in the ensuing description of operation. Thus it will beseen how in, the preferred embodiment of inyinvention, the subscriber ata calling substation upon initiation of a call In such lectors O towhich it has access. The subscriber at A now operates his calling device1 to e'fiect two interruptions of impulse springs 2, this number ofimpulses corresponding to the first digit of tlie called substationnumber. Responsive to the said two interruptions, relay PR retracts itsarmature two times causing two interruptions of its alternate contact23, and thereby two interruptions of the initial or first energizmgcircuit for MR3. As previously stated these interruptions do not allowthe retraction of the armature of MRR, due to the second circuit beingmaintained closed through alternate contact 27 of RR. Also upon eachdencrgization of PR, its normal contact 22 is closed, transmitting aprimary directive impulse through primary magnet PM. These impulsestraverse a path for said normal contact 22, alternate contact 29, normalcontact 30, and the winding of PM to battery. These two impulses throughmagnet PM. efiect two primary steps of the wipers 31, 32, 33 to selectthe second group corresponding to J In systems of the present character,such as employ two dimension switches, that is, switche in which thewipers are adjusted primarily to select a group of contacts, andthereafter to automatically select an idle set of contacts in the group,a slow acting secondary relay has been provided which is adapted due toits special construction to maintain its armature attracted while theprimary relay is operating, and upon cessation of the primary relayoperations,.such secondary relay retracts its armature to bring about aSecondary circuit change to client the automatic selection of an idleset of contacts in the selected group. Such a slow acting relaynecessarily involves a special construction, either by the use of acopper sleeve about its core, or a non-inductivewinding in shunt of itsmagnet winding. In the present invention I eliminate the use of suchspecially constructed secondary relays, and employ an ordinaryquicl;acting relay SR. To maintain the armature of this quick acting relayenergized while the primary relay is operating, (although its circuit isinterrupted each tune the primary relay operates), I so connect it incircuit with the primary magnet PM that the primary impulses travelthrough the winding of both the primary magnet and secondary relay, andafter each impulse the self-induced current of SR flows through thewinding of PM and through the winding of the secondary relay andmaintains the armature of attracted, during the short period ofinterruption of its circuit, loctween the transmission of the impulses.l

i also preferably wind relay SE to a som paratively high resistance withrelation to RM, thereby securing a most efiective holding operation ofSR.

Referring now to the arrangement of the first selector C, upon the firstimpulse from relay PR flowing through the winding of both the relay SRand magnet PM, normal contact 37 of SR is interrupted, and maintainedinterrupted during the transmission of the primary impulses. Uponcessation of such impulses, relay SR allows its armatureto retract,thereby closing normal contact 37 and establishing a circuit for itsrelay TR traced from ground at normal contact 37, alternate contact 38,38, normal contact 39 and the winding of PR to battery. Relay TRtherefore closes its alternate contact 40, establishing an operatingcircuit for magnet SM, whereby wipers 31, 32, 33 are stepped intoengagement with the first set of contacts 34, 35, 36 of the selectedgroup. Assuming the first set of contacts leads to a busy secondselector D, its test contact 34 will be grounded through one of themultiple contacts, and wiper 31, and normally grounded contact 41 of theswitch connected thereto. Therefore, although the initial energizingcircuit for relay TR was interrupted by the opening of normal contact 39of SON, this maintaining circuit from test contact 34, flows over a pathincluding wiper 31, alternate contact 41, alternate contact 42, and thewinding of TR to battery whereby said relay maintains its armatureattracted and magnet SM continues to advance wipers until an idle set ofcontacts is reached. Assuming the third set shown is the first idle setreached, its test contact 34 has'no busy potential or ground connectedthereto so that relay TR deenergizes interrupting its alternate contact40, whereby the circuit for SM is interrupted, rendering the wipers 31inert. It will be noted that while the wipers are traveling over thecontacts, talking wipers 32, 33 have their circuit interrupted at normalcontacts 43, 44, thus preventing interference with'the existingconnections.

Upon retraction of the armature of TR, its normal contact 41 is closed,placing a ground or busy potential upon the terminals 34 of the selectedtrunk. This ground connection is also effective to cause energization ofrelay RR of selected switch D, the circuit being traced over itsconductor 45, normal contact 46, and the winding of RR to batterycausing the energization thereof, whereby itsalternate contact 47 isclosed, establishing a locking circuit for itself independent of thenormal contact 46. Thus, responsive to the first operation of callingdevice 1, the line of thecalling substation has been extended to asecond selector D,

.. which has access to the connector switches of the second thousandgroup which ingroup J of Fig. 3.

eludes the line of the called substation whose number it will beremembered is 2343. The subscriber at station A now operates callingdevice 1 to effect three operations of primary relay PR, the number ofoperations corresponding to the digit value of the second or hundredsdigit of the called substation number. Responsive to said threeoperations of PR, three primary ordirective impulses aretransmitted-through magnet PM 7|: and secondary relay SR of switch D,these impulses following a path from normal contact 22 of PR, alternatecontact 29, normal contact 43, wiper 32, contact 35, primary conductorof switch D, conductor 48, normal contact 49 and the winding of SR andPM in parallel to battery. The first impulse through SR causes theinterruption of itsnormal contact 50 which is maintained opened as longas the directive impulses are being transmitted through the windings ofSR and PM The maintaining of the armature of SR attracted during thetransmission of primary impulses, is brought about by the self-inducedcurrent flow through SR and PM in series as in the case of the firstselector C as previously described. The said three impulses through themagnet PM are eifective to step wipers 51, 52,53 to the third group ofcontacts 54, 55, 56, which group corresponds to i This third group ofcontacts leads to connector switches E associated with the thirdhundreds group of lines in the second thousands group, which includesthe line of the called substation.

After the transmission of the said three primary impulses, SR retractsits armature closing its normal contact 50 to eflect the v operation ofrelay TR the circuit therefor being traced from ground at said normalcontact 50, alternate contacts 57 57, normal contact 58, the winding ofTR to battery. Alternate contact 59 of TR is accordingly closed,establishing an energizing circuit for SM whereby wipers 51', 52, 53 areadvanced into engagement with the first set of contacts 54, 55, 56 ofthe selected group. Assuming this first set leads to a busy connector E,its test contact 54 will be at. a ground or busy potential through oneof its multiple contacts 54, a wiper 51 of a switch D and its normalcontact 60 to ground, so that a maintaining circuit for TR is closed.This circuit may be traced from said ground at con- 12(/ tact 54, wiper51, alternate contact 60, alternate contact 61, and the winding of TR tobattery, (as it will be noted that the-initial circuit for TR isinterrupted at normal contact '58 of SON). Magnet SM therefore advancesthe. wipers another step and in fact continues to do so until an idlesetof con-.

tacts are reached, such set having no ground or busy potential upon itstest contact 54. Assuming the third set illustrated is-the first idleset reached, there being no maintaining circuit for TR, it retracts itsarmature, interrupting the. circuit for SR and rendering the wipersinert. Due to the interruption of the circuit for talking wipers 52, 53,at normal contacts 62, 63, while said wipers are in their secondarytravel, any existing connections over which these wipers move are notinterfered with.

From the foregoing it will be seen that the subscriber in response tothesecond movement of his dial has selected an idle connector switch havingaccess to the terminals of the wanted line, the connection being tracedover the heavily marked conductors.

It will be noted that upon selection of connector E and upon retractionof the armature of TR a ground or busy potential from normal contact isconnected to the selected test contact 54, thus preventing any otherswitch from connecting to the selected connector E. This groundconnection is also effective to energize relay Ttlt of switch E, circuitbeing traced over test conductor 64, normal contact 65, and the windingof Rit to battery, causing its energizatio-n, but without any efiect atthis time. The subscriber at A operates his calling device 1 to sheettour interruptions of his line circuit resulting in four operations ofthe primary relay lP'lt. Four impulses are therefore transmitted fromnormal contact 22, over the primary conductor to connector'lfl, thenover normal contact 66, conductor 67, normal conlid tact 68 toconnection 69 at which point the impulses divide and include thewindings of TM and hill. From point 69 said impulses are passed throughnormal contact and the winding of'lPh l to battery, while the other pathfor said impulse includes conductor Tl and the winding 01 SE to battery.The said four impulses flowing through the mag nct PM eliect fourprimary steps of wipers 72, 73, 74, to select the fourth group ofcontacts 2'5, 76. 7t", which group corresponds to group J4- illustratedin Fig. 3 and which group includes the terminals of the called line.

The first impulse flowing through secondary relay SR causes itsenergiaation where ,by it closes its alternate contact 7 8 to cause theenergization of secondary relay SR which by interrupting its normalcontact 79 prevents a premature operation oi switch relay SW whencontact lPQli closes on the first primary step of the switch. [is in thecase of the other switches, the seltinduced current flow from SR throughthe winding cit PM and of SR (which it will be noted is connected inparallel with Phl causes @lt to hold its armature attracted andtherebymaintain its contact 78 closed during the transmission of the primaryimpulses. Upon cessation of said impulses, SR interrupts its contact 78,allowing SE to restore.v Upon restoration of SR a circuit for SW isclosed traced from ground at PON normal contacts "(9, 80, the winding ofSWV, to battery, whereby its alternate contact is closed, establishing alocking circuit to ground at alternate contact The energization ofswitching relay SW interrupts normal contact 70 and closes alternatecontact 70, whereby primary magnet PM is disconnected and secondarymagnet SM is connected with the primary conductor. The subscriber atsubstation A now operates dial 1 to effect three operations of theprimary relay PR, whereby three impulses of current are transmitted fromnormal contact 22 of PR over the primary conductor and through thewinding of SM and SR in parallel to bat tery. This final set of primaryimpulses through 8M and SR varies, in that the first impulse of thefinal set flows through normal contact 68 of SON while any followingprimary impulses of the final set flow through alternate contact of EBRdue to the interruption of normal contact 68 of SDN upon the firstsecondary step of the switch. Referring now more in detail to the flowof these impulses, the first one flows over the primary conductor,through normal contact- 66 of relay @L, conductor 67, normal contact. 68to point 69, part of the current of the first impulse flowing from thereover con- (hector '71 and the winding of slt to battery, while part ofthe current flows from point 69 over alternate contact 70, normalcontact 81, the winding of SM and normal contact 82 to battery.Responsive to the energization of Falt by the first said impulse, itsalternate contact 78 is closed establishing an energiaing circuit for SRso that when normal contact 68 interrupts upon the first secondary stepof the switch. the following two impulses of the last primary set flowfrom normal contact 66 through alternate contact 110 to SR, part of thecurrent l'low ing through SR and part over conductor 71., alternatecontact 70 and Ell l as before. These three impulses cause threeoperations of SM whereby wipers 72, 78, 74-. are ad vanced threesecondary steps to engage the third set oi terminals 75, 76, 77, whichare the terminals oil the line of called substation l Due to thetransmission of those three impulses through SR and the self-inducedcurrent flow through @Tt and Sit l which are connected in parallel. saidrelay holds its armature attracted and its alternate contact 78 closed.SR therefore is energized until after the transmission of the last oneof the said three impulses, whereby its arinature is retracted,interrupting the circuit for SR which now restores interrupting itsalternate contact 7 9 and thereby opening the energizing circuit for theslow acting test interrupter relay TI. This relay (TI) being slowacting-'maintains its armature hli attracted momentarily so that if theline connected with is idle, a second energizing circuit is closedthrough its winding to maintain its armature attracted as will bepointed out. It will be noted that although the test circuit leading totest wiper 7 2 is closed at alternate contact 8 1 of relay TI during thesecondary travel of the wipers, this test circuit is interrupted atnormal contact 85 of SR due to the fact that SR is energized during thesecondary travel of the switch.

In the present embodiment of my invention I have preferably arranged myconnector switch so that if-connection is made to the terminals of abusy line, a characteristic busy signal is transmitted to thecalling-substation, while if the line connected with is idle, ringingcurrent is automatically con-' nected to the terminals thereof tooperate the call signal at the called substation. Up

to the period in the operation of the system busy.

Called Zine idZe.Assuming that the line connected with is idle, uponrestoration of SR its normal contact 85 is closed connecting the lowerwinding of line test relay.

LT in circuit with the test terminal 7 5 of the called line before slowacting relay TI has a chance to retract its armature. This circuit maybe traced on one hand from wiper 72, through alternate contact 84, thelower winding of LT, normal contact 85, to ground at alternate contact86 of BB and on the other hand this test circuit is traced from wiper72, through terminal 75, contact 0N and winding CO -to battery. Theserelays LT and C0 are thus connected in series and are both energizedover the circuit just traced. The energization of CO removes thesubstation control of its line switch B while due to the closing ofalternate contact 88 of LT, a circuit is closed through the winding ofslow acting relay TI, causing it to maintain its armature attracted andits alternate contact" 84, which is included. in the test circuit,closed. Due 'to the closing of alternate contact 89 of, LT, a lockingcircuit through its upper winding is established, traced from batterythrough said upper winding, current reducing resistance 90, alternatecontacts 91, 89, conductor 92 to ground at alternate contact 86 of BB Bythe closing of alternate contact 93 of LT, its lower winding is shortcircuited due to the direct ground connection traced from alternatecontact 86, conductor 92, to contact 93,

ing of alternate contact 95 of H, establishes an energizing circuit forrelay FF, Whereby it periodically attracts its armature due to theinterruptions of its circuit by the rotation of interrupter I. Thisenergizing circuit for FF is traced from ground at normal contact 96 ofrelay DR, alternate contact 95, winding of FF and interrupter I tobattery.

Each time relay FF attracts its armature, its alternate contacts 97, 98are closed, con necting the ringing generator G in bridgeof theterminals of the called line, whereby the call bell at substation F isoperated. This circuit may be traced from the upper terminal ofgenerator G, alternate contact 97 wiper 73, terminal 76, over thecalling line including the call bell and condenser of substation F,returning over line terminal 77, wiper 74, conductor 99 and alternatecontact 98 to the other terminal of gen-.

' erator Gr.

Upon each retraction of the armature of FF, its normal contacts 97, 98are closed, whereby control relay GR is connected in bridge of theterminals of the called line, but as long as the receiver remains uponthe switch hook at the called substation, due to the interposition ofthe condenser thereat,

no path for the fiow of steady current through control relay CR exists,but upon the removal of the receiver at the called substation, a pathfor steady current is provided to cause the energization thereof. Thispath may be traced from ground through the upper winding of CR,alternate contact 100, normal contact 97, wiper 73, terminal 76 over thecalled line and substation F of which the receiver has been,re-

moved, returning over the line terminal 77,

wiper 74, conductor 99, normal contact 98, alternate contact 101, andthe lower windmg of OR to battery. Thus with the relay FF deenergizedand the receiver removed at substation F, control relay CR energizes toautomatically bring about the disconnection of ringing current in thecalled line as=w1ll be described.

Upon energization of CR caused by the response of the called subscriber,its alternate contact 102 being closed, relay CL energizes closing itsalternate contact 103, whereby disconnect relay DR is energizedinterrupting its normal contact 96 and thereby rendering relay FF inert.By the closing of alternate contact 104 of DR, a locking circuitforitself is established to ground at PON and by the closing of its.alternate contact 96, switching relay SW is maintained energized.

By the closing of alternate contact 66 and 105, of closing relay CL, thetalking circuit between the calling and called substation has beenestablished, said circuit being traced over the heavily marked primaryand secondary conductors, condensers 106, 107 being interposed at firstselector C. Talking battery for the calling line is provided throughprimary relay PR, while talking battery for the called line is providedthrough the control relay OR of connector E.

ReZease.After the subscribers have finished conversation they mayefiectthe release of the switches used in establishing the connection byrestoring their receivers upon their respective switchhooks. In thepresent embodiment of my invention I preferably eflect the release ofthe connector E by the called subscriber, while the calling subscribercauses the restoration of switches B, C and D. Assuming-the callingsubscriber is the first to replace his receiver upon its switch hook,the circuit for relay PR is interrupted causing its restoration. Thiscauses the interruption of contact 23, where by one of the oaths forcurrent for the main release relay MRR is interrupted, and as thecurrent flowing through the second path which includes resistance 28 isnot suiiicient of itself to maintain the armature of MBR attracted, saidrelay MRR retracts its armature interrupting its alternate contact 26allowing relay RR to restore. lUpon restoration of Bil-It, normalcontact 42 is closed, establishing an energizing or release circuit forrelay TR traced from ground at normal contact 37 of SR, alternatecontacts 38, 38 normal contact 42 and the winding of TR to batterycausing its energization. Alternate contact 40 is therefore closed,whereby magnet SM advances the wipers of the switch in a secondarydirection until'they have passed beyond .the last contact of the groupwhereby they are automatically restored in a manner as previouslydescribed,

the contacting ends of the wipers taking the path indicated by thearrows in Fig. 3, as already pointed out. Upon restoration ofalternate-contact 38 of POE, relay TR deenergises, interrupting thecircuit of SM. Following the restoration of switch C, switch B isrestored, this being brought about by the interruption of alternatecontact 24 of PON of switch C, thus causing the restoration of relay LRwhich it will be remembered has been held energized through saidalternate contact 24:. Upon restoration .of LR, its normal contact 13 isclosed, es-

tablishing an energizing circuit for GO 3 which upon attracting itsarmature withdraws check pawl 7 from engagement with ratchet 6, and asrelay LR is deenerglzed and its pawl 8 out of engagement with ratchet 0,the wipers of switch B restore to normal Upon restoration of thealternate contact ON, relay CO restores and switch B being at normal,the line at substation A is available for use in establishing otherconnections.

The release of second selector D is brought about by theenergizationof'TR when its release energization occurs at the release offirst selector C. That is, upon the release energization of TR, itsnormal contact 41 is interrupted, interrupting the circuit for relay RBof second selector D, causing its deenergization. Its normal contact 61is therefore closed, establishing a release circuit for TR traced fromground at normal contact 50 of SR alternate contacts 57 57 normalcontact 61, and the winding of TR to battery. Alternate contact 59 istherefore closed, establishing a release circuit for SM switch D untilit is at normal, this ground connection extending from normal contact106 of .RR, alternate contact 46, test conductor 45 .and its contact 34.Upon restoration of PON of switch D, the circuit of TR is interrupted,causing its restoration and the interruption of the release circuit forSM Upon restoration of switch D and the removal of the ground or busypotential from its .test conductor 45, said switch is available for usein establishing other connections.

The subscriber at F upon replacing his receiver upon its switch hook,interrupts the circuit for control relay CR whereby it deenergizesinterrupting its alternate contact 102 and causing restoration of relayCL. Normal contact 103 of CL is therefore closed establishing anenergizing circuit for BB traced from ground .at normal contact 103,alternate contact 115, and the winding of RR to "battery. Relay RR istherefore energized whereby its normal contact 65 is in- .ter-ruptedallowing restoration of RR and its alternate contacts 86, 91 beingthereby interrupted, relay, LT restores. By the interruptlonlofalternate contacts 88 and 88 of LT, relays H and TI restore and thecircuit for cut-oil relay (10 having been interrupted, said relay alsorestores to normal.

,R-eturning now to release relay BB due to the closure of its alternatecontacts 81, 82, a release circuit for SM is established whereby thewipers of connector E are advanced in a secondary direction beyond thelast contact in the bank whereby they are automatically restored. Uponrestoration of PON the locking circuit for disconnect relay DR isinterrupted causing its restoration whereby its alternate contact 115being in terrupted, relay BB is deenergized. Connector E being at normalis now available for use in establishing other connections.

Called Zine busy.In the foregoing connection it is assumed that thecalled'line was found idle upon connection made therewith, and thereforeI will now describe the operation upon connection to the terminals of abusy line. Up to the last secondary circuit change at the connectorswitch, the operation of the system is the same whether the lineconnected with is idle or busy. It will be remembered that up to thissaid period, and referring now to connector switch E, relays R SlV. andTI, have their armatures attracted, relays RR and SW being energizedover locking circuits, while relay TI is momentarily holding itsarmature attracted after the deenergization of secondary relay SE. Theline L being busy, its test terminals will have a busy or groundpotential thereon, either from ground at alternate con tact 18 of lineswitch B if the line be calling, or through alternate contact 93 ofrelay LT of a connector switch E if the line be a called line.Therefore, relay LT of switch E being connected at the upper terminal ofits lower winding to ground at alternate con tact 86 of EH and the otherterminal of the lower winding being connected through wiper 72 to groundat the engaged test terminal 75, relay LT does not energize, andtherefore no substitute energizing circuit for the slow acting relay TIbeing provided, the armature of TI retracts interrupting its alternatecontact 84. Relay LT having failed to come up, relay H does not energizeso that busy back BB remains connected to the primary conductor ofswitch E, traced from BB alternate contact 109, normal contacts 94, 110and 66, back over the heavily marked primary conductor through receiverof the calling substation, returning over the heavily marked secondaryconductor, the winding of PR to the negative terminal of battery whichis of course connected to'BB the path just traced being a closedsecondary circuit. By the undulations of current induced in thissecondary circuit, a characteristic signal is transmitted to the callingsub station and the calling subscriber in response to said busy signalreplaces his receiver upon its switch hook, thereby effecting therelease of all of the switches used in establishing the connection. Therelease of switches B, C and D is as previously described.

The release of connector E is effected responsive to the interruption ofthe holding circuit of BB when relay TR of secondary selector Denergizes andinterrupts its normal contact 60. BB therefore restoresclosing its normal contact 113, whereby a circuit for BB is establishedfrom battery through the winding of BB normal contact 113 and PON toground. RR therefore closes its alternate contacts 81, 82, effecting arelease operation of SM as before described, caus ing the restoration ofswitch E. Upon restoration of PON the holding circuit for RR and SW isinterrupted, allowing their restoration and switch E being restored, isavailable for use in establishing other connections.

Figure 4.-In the above figure, I have illus trated a modified circuitarrangement of that illustrated in Fig. 1, part 1. In the present figurethose parts which correspond to parts in Fig. 1, part 1, are indicatedby like reference characters but with the sufiix added, except in a fewinstances where different suffixes are added as will be apparent from aninspection of the drawing. The arrangement of Fig. 4 differs in onerespect from Fig. 1, part 1, in that the main release relay MRI?maintains its armature attracted during the vibration ofthe primaryrelay PR by impulses through alternate contact 23* of PR and impulses ofself-induced current from MRR through its winding and the comparativelylow resistance impedance coil 28*. In other words, while PR isenergized, MRR is maintained energized through the first energizing pathwhich includes alternate contact 23 and al ternate contact 25*. Uponeach deenergiza tion of PR, that is, each momentary deenergization whileit is operating to transmit im pulses, as armature 23 is restoring, thethree contacts 23*, and 23 are momentarily in engagement so that thereis a flow of current from battery through the windings of MRR and 28 toground at alternate contact 25 As armature contact 23* disengages fromcontact 23 the circuit through 25 is interrupted, and due to the factthat the winding of 28 is of low resistance and self-induction comparedto the winding of MRR"; a dis charge of current from MRR due to thedeclining magnetic field, flows through the closed circuit including thewinding of MRR and 28 This impulse of discharge current being at a time.when the first energizing circuit for MRR is interrupted, the armatureof MRR is maintained attracted momentarily or until the first saidcircuit through MRR is closed again by the reenergization of PR and theensuing closure of its contacts 23 Thus while relay PR is vibrating at apredetermined speed, due to the establishment of the first energizingcurrent for MRR, and the closure of its second or discharge circuit, thearmature of MRR is maintained in its attracted position, whereby thecontact 26* is maintained closed, and release relay RR held energized.

As to the operation of Fig. 4, the selection of an idle switch G isaccomplished as in Fig. 1, part 1. Assuming the subscriber at A hasremoved his receiver from its hook and switch B has selected the firstselector (1*, relay PR is energized to maintain the line relay LEenergized as previously described. The closing of alternate contact 2!-23 of PR establishes an energizing circuit for ldRl-t as before wherebyits alternate contact 26 is closed causing the energization of RR*. Thesubscriber at A now operates his dial in the act of calling" the wantedline, and therefore interrupts the circuit of PR a number of times,according.

to the number of the called line. Upon each deenergization of PR*,. itsnormal contact 22" is closed to effect the operation of magnet PM aspreviously described. Also upon each deenergization of PR its armaturecontact 23 restores to normal and in its restoration the three contacts23*, 23 and 23 are momentarily closed whereby there is a momentary flowof current through the winding of the low resistance impedance coil 28*.Upon the-interruption of this said circuit through; 28 and MRR caused bythe interruption of contact 23 due to the declining magnetic field ofMRR there is a: flow of current through its windings in the samedirection as its initial or energizing circuit, the flow dischargingthrough the winding of MRI? and causing relay MRR to maintain itsarmature attracted until its first energizing path is again closedthrough: contacts 28*, 23 It will be apparent from this that as long asrelay 1 B is rapidly vibrating its armature, relay MRR will maintain itsarmature attracted so that BB is kept energized to. prevent the releaseof the switch. Upon restoration of the armature of PR for any extendedperiod, the

circuit of MRR is interrupted long enough tion l have embodied it in apreferred type to allow the retraction of its armature and thereby causethe release of the switch. The rest of the operation of switch (3 issimilar to that of switch (1 and it is believed that from the foregoingdescription-of 0 its full operation including its release and therelease of B will be apparent.

Referring again'to line switch B, it might be added that this switch ispreferably arranged whereby should all of the associated firstselectorsC be busy, it will automatically step its wipers 9, 12 and 16 to thelast contact 17, 18", 1:9 and there being no ground upon contact 19 thecircuits for CO and LR are interrupted causing the imme-;

diate deiner ization of CO, although the armature of R is maintainedattracted due to the sluggish or slow acting construction of LB. Upondeenergization of CO its normal contacts 10, 11 are closed, whereby acircuit for LR is established, traced from battery through the windingof LR, its alternate contact 20, wiper 16, contact 19, contact17, wiper9, normal contact 10, line L and substation A, normal contact 11, wiper12, contact 18, and the Winding of BB to ground. This circuit iseffective to maintai-n relay LR energized, While a characteristic signalis transmitted over the path described by busy device BB. The subscriberi at A knows that all trunks are busy, and thereafter replaces hisreceiver upon its switch hook interrupting the circuit of LB a andcausing its restoration. Its normal contact 13 is therefore closed,establishing an energizing circuit for CO whereby CO having energizedand LR deenergized, thev wipers of switch B restore to normal causingthe interruption of alternate contact ON and the restoration of relayCO.

In connection with the multiple circuits of the different switches suchas that of the relay SR and magnet PM of first selector C, I I havefound that by the use of an ordinary standard Kellogg relay of 500 ohms,and an electro-magnet such as vis ordinarily employed for drivinselector switches with a resistance of -50 0 me, very satisfactory results are secured. With this arrangement the self-induction of the highresistance relay is sufficient to set up a' continued flow through therelay and magnet windings in series and thereby maintain the armature ofthe relay momentarily attracted after its initial energizing circuit hasbeen interrupted. The above figures are given for the purpose ofillustration and it is to be understood that the resistances may bevaried to ,theextent that the self-induction of one electromagnet issufficient to overcome that ,of the other and cause such a flow throughthe winding of the relay as to maintain its armature momentarilyattracted after its initial energizing circuit is interrupted.

For the purpose of illustrating my invenof automatic telephone systembut it is to be understood that my invention is not limited to the exactarrangement shown, and I contemplate applying it in other ways, and

therefore I do not desire to be limited to the fexact arrangements shownand described but ple circuit including said magnet and relay, 1 meansadapted for transmitting impulses of current over said multiple circuitto operate said magnet and relay, the winding of said magnet and relaybeing so related that a discharge of current from said relay, after eachimpulse, flows through the windings of said relay and magnet to maintainthe armature of the relay attracted between impulses, and a secondarycircuit controlled through contacts of said relay.

2. A selector switch comprising a primary magnet, a quick-actingsecondary relay, a multiple circuit including said primary magnet andsaid secondary relay, means adapted for transmitting impulses of currentover said multiple circuit whereby said primary magnet is operated andsaid secondary relay energized to attract its armature, the

windings of said primary magnet and secondary relay being so relatedthat a discharge of current from said relay, after each impulse, flowsthrough the windings of said secondary relay and magnet to maintain thearmatureofthe relay attracted between impulses, and a secondary circuiteffective upon retraction of said armature upon cessation of theimpulses.

3. A selector switch comprising a primary relay, a primary magnet and aquick-acting secondary relay, a multiple circuit including a source ofcurrent said primary magnet and said secondary relay, meansfor'transmitting impulses from said primary relay over said multiplecircuit whereby said primary magnet is operated to step the switch andsaid secondary relay energized to attract its armature, the windings ofsaid primary magnet and secondary relay being so related that adischarge of current from said relay after each impulse flows throughthe winding of said secondary relay and magnet to maintain the armatureof the relay attracted between impulses, a secondary magnet andsecondary circuit for causing operation thereof effective uponretraction pf said armature.

4. A selector switch comprising a primary relay, a primary magnet, animpulse circuit including said magnet and contacts of said primaryrelay, a quick-acting secondary relay connected in multiple circuit withsaid primary magnet and adapted to receive said primary impulses wherebyits armature is attracted and whereby a discharge of current from itswinding through said primary magnet after each impulse causes thearmature of the relay to remain attracted, said armature retracting uponcessation of said primary impulses, a secondary magnet for said switch,and a secondary circuit for operating said magnet effective responsiveto retraction of said armature.

5; A telephone system comprising a metallic circuit telephone line,selector and connector switches, a primary relay, a primary magnet andquick-acting secondary relay for each of said selectors and connectors,a multiplecircuit for each of said selectors and connectors including asource of current and its said primary magnet and secondary relay, meansfor transmitting imw pulses from a primary relay over the multiplecircuits -of selector and connector switches in extending the circuit ofsaid line, the windings ,of each primary magnet and secondary relaybeing so related that impulses through the secondary relay assisted bythe discharge from its winding through said winding and the primarymagnet aftereach impulse, maintain the armature of the secondary relayattracted during the transmission of the impulses, and a secondarycircuit for each switch effective upon retraction of the armature of theassociated secondary relay.

6. A selector switch comprising primary, secondary and release magnets,a primary relay, a quick-acting secondary relay, a multiple circuitincluding said primary magnet and secondary relay, an impulse circuitcontrolled by said primary relay f or transmitting impulses of currentover said multiple circuit to operate the included magnet and relay, thewindings of said magnet and relay being so regulated that a dischargeof.

current from said relay, after each'impulse, flows through the windingsof said relay and magnet to maintain the armature of the relay attractedbetween impulses, a secondary circuit for said secondary magneteffective upon retraction of said armature upon cessation of theimpulses,'and means for operating said release magnet also controlled bysaid primary relay. I

7 A telephone system comprising a calling line, a selector switchconnected thereto,

a primary relay connected in bridge of said line and adapted to beoperated. over the metallic circuit thereof, a quick-acting releaserelay, an energizing circuit therefor adapted to be closed when saidprimary relay is energized and interrupted responsive to impulseoperations thereof, a second circuit for said release relay and meansfor connecting it to maintain the armature of said release relayattracted while its first circuit is being interrupted, a primary magnetand quick-acting secondary relay connected in multiple circuit with animpulse contact of said primary relay, the inductance of said relaybeing greater than said magnet whereby said secondary relay maintainsits armature attracted during the transmission of primary impulses, asecondary magnet, and a secondary circuit for rendering said magneteffective upon cessation of the primary impulses and the ensuingretraction of the secondary relay armature.

8. A connector switch comprising primary and secondary magnets, aquick-acting secondary relay, a multiple circuit including ings of saidmagnet and relay to maintain the relay armature attracted betweenimpulses, a secondary circuit adapted to be closed responsive toretraction of said armature upon cessation of the impulses whereby saidprimary magnet is replaced by said secondary magnet in multiple relationto the secondary relay to recelve further impulses.

9. A connector switch including primary and secondary magnets, aquick-acting secondary relay, a multiple circuit including said primarymagnet and secondary relay,

the windings of said multiply connected magnet and relay being sorelated that a discharge of current from said relay, after eachdirective impulse, flows through the windings of said magnet and relayto maintain the relay armature attracted between impulses, a secondarycircuit adapted to be closed upon retraction of said armature uponcessation of the impulses, a switching relay operated responsive to saidsecondary circuit closure, whereby said primary magnet is replaced bysaid secondary magnet in multiple relation to the secondary relay toreceive further impulses.

10. The combination with a switch operating magnet, of a relay, meansfor transmitting impulses of current over a multiple circuit includingthe windings of said magnet and relay to cause their energizations, oneof said windings being so related to the other that upon termination ofeach impulse a self-induced current flow traverses both of said windingsto maintain the armature of the relay attracted between impulses, and asecondary circuit controlled through contacts of said relay.

11. The combination with a switch operating primary magnet, of asecondary relay, means for transmitting impulses of current over amultiple circuit including the windings of said magnet and relay tocause their energizations, one of said windings being so related to theother that upon termination of each impulse a self-induced current flowtraverses both of said windings to maintain the armature of the relayattracted between impulses, and a secondary circuit effective uponretraction of said armature upon cessation of the impulses. v v

12. The combination with a primary relay, of a switch operating primarymagnet and secondary relay, means for transmitting impulses of currentover a multiple circuit including the windings of the last said magnetand relay to cause their energization whereby said primary magnet iscorrespondingly operated and said secondary relay attracts its armature,one of said windings being so related to the other that upon terminationof each impulse a self-induced current flow traverses both the saidwindings to maintain the armature of the relay attractedbetweenimpulses, a secondary magnot, and a secondary circuit-effectivefor causing the operation of said secondary magnet upon retraction ofthe secondary relay armature when said impulses cease.

- 13. The combination with a metallic circuit telephone line, ofselector and connector switches for extending the circuit thereof, aprimary relay, a primary magnet and secondary relay for each of saidswitches, a multiple circuit for each of said switches including thewindings ofits primary magnet and secondary relay, means foroperattermination of each impulse a self-induced current flow traversesboth windings to maintain the armature of the relay attracted betweenimpulses, and a secondary circuit for each switch effective uponretraction of the armature of the associated secondary relay.-

14. The combination with primary, secondary and release magnets, of' aprimary relay and a secondary relay, means for operating said primaryrelay for transmitting current impulses over a multiple circuitincluding the windings of said primary mag net and secondary relay, oneof said windings being so related to the other that upon termination ofeach impulse a self-induced current flow traverses both the saidwindings to maintain the relay armature attracted between impulses, acircuit for said secondary magnet effective upon retraction of saidarmature upon, cessation of the impulses, and circuit connections foroperating said release magnet, also controlled by said primary relay.

15. A connector switch comprising primary and secondary magnets, and asecondary relay, a multiple circuit including the windings of saidprimary magnet and secondary relay adapted for recelvlng directiveimpulses, the windings of the last said magnet and relay being sorelated that upon termination of each impulse a self-induced currentflow traverses both of said windings to maintain the armature of therelay attracted between impulses, and a secondary circuit adapted to beclosed responsive to retraction of said armature upon cessation of theimpulses whereby said prlmary magnet s replaced by said secondary magnetin multiple relation to the secondary relay to receive further impulses.

16. A connector switch including primary ated responsive to saidsecondary circuit closure whereby said primary magnet is re- 15 placedby said secondary magnet in multiple relation to the secondary relay toreceive further directive impulses.

Signed by me at Chicago, county of Cook and State of Illinois, in thepresence of two 20 witnesses.

CHARLES s. WINSTON.

Witnesses G. E. MUELLER, vB. OBRIEN.

